The Nobel prize medal was made from 23 carat gold before 1980 while the newer ones are 18 carat green gold plated with 24 carat goldWikiCommons

A Nobel prize medal for medicine will be auctioned at Sotheby's and the money raised will be used to train scientists.

The medal given to German Jewish refugee Hans Krebs in 1953 for his discovery of the citric acid cycle was put on sale by Krebs's son John, who is a member of Britain's House of Lords.

The medal will be on sale on 14 July and has a pre-auction estimate of £250,000-£300,000 ($385,000-$462,000), reports Reuters.

The proceeds will be used by The Sir Hans Krebs Trust for its work "to provide grants for the support of refugee scientists and the training of young scientists in the biomedical sciences," Sotheby's said.

Krebs fled Nazi Germany in the early 1930s and settled in Britain, where he resumed his work as a scientist.

"My father was a passionate believer in the importance of training the next generation. I believe that he would have thoroughly approved of the creation of the Trust by the sale of his Medal," John Krebs said in a statement.

The Nobel Prize medals were made from 23 carat gold before 1980 while the newer ones are 18 carat green gold plated with 24 carat gold.

The Nobel medals have had the same size and design since 1902. The diameter of the medal is 66mm but the weight and thickness varies with the price of gold.

The average Nobel Prize medal is 175g with a thickness ranging from 2.4-5.2mm.

Past instances of sale

The Nobel prize for economics won by Simon Kuznets in 1971 and for chemistry won by Heinrich Wieland in 1927 were both sold in auctions by descendants for almost $400,000.

Rare cases where the recipient himself/herself put up the medal for sale, include the recent auction of the 1988 medal by experimental physicist 92-year-old Leon Lederman and James Watson's medal for the discovery of DNA.

Lederman won the Nobel prize for physics with two other scientists for discovering a subatomic particle called the muon neutrino.

Watson sold his medal after his fall from grace in 2007 for racist remarks linking intelligence to race in his reference to Africa and its bleak prospects.